CN107930839B

CN107930839B - Gravity separation-flotation combined separation method for graphite and silicon

Info

Publication number: CN107930839B
Application number: CN201711191861.2A
Authority: CN
Inventors: 刘颀; 张明青; 江宏富; 郄丽曼
Original assignee: Jiangsu Zhongneng Polysilicon Technology Development Co ltd; China University of Mining and Technology CUMT
Current assignee: Jiangsu Zhongneng Polysilicon Technology Development Co ltd; China University of Mining and Technology CUMT
Priority date: 2017-11-24
Filing date: 2017-11-24
Publication date: 2020-12-29
Anticipated expiration: 2037-11-24
Also published as: CN107930839A

Abstract

The invention discloses a gravity separation-flotation combined separation method for graphite and silicon in waste graphite assemblies produced from silicon crystals, aiming at the waste graphite assemblies produced in the silicon crystal production process, which comprises the following steps: crushing, screening, gravity separation, ore grinding and flotation. The content of the graphite carbon recovered by the method is more than 97%, and the recovery rate is more than 85%; the silicon content of the silicon product is more than 98 percent, and the recovery rate is more than 90 percent. The method has low cost and stable and reliable product quality, can realize continuous large-scale production, and realizes the cyclic utilization of carbon and silicon resources.

Description

Gravity separation-flotation combined separation method for graphite and silicon

Technical Field

The invention relates to the crossing field of mineral processing and solid waste treatment, in particular to a method for separating and recovering graphite and silicon in waste graphite components in a silicon crystal production process by adopting reselection and flotation.

Background

Currently, silicon crystal yield is increasing with the great increase in market demand for silicon crystals. During the silicon crystal reduction production process, various graphite assembly waste materials such as carbon head materials, graphite cap bases, graphite clamping flaps and the like can be continuously discharged. These components are surface enriched with a portion of the silicon material during the production process.

The graphite in the graphite components has high purity, and the silicon material with enriched surface has high added value, so the effective separation and recovery of the graphite and the silicon material have obvious economic and environmental benefits. At present, the treatment of the graphite waste is not reported. In practice, silicon crystal manufacturers sell such graphite waste. And the recovery enterprise recovers part of large-particle silicon materials by adopting a manual crushing and manual sorting mode. Then removing carbon on the surface of the silicon material by means of multiple acid washing, strong alkali or strong oxidant treatment and the like, and then cleaning and drying to obtain the product. The rest waste graphite has extremely high carbon content and high heat generation, and is often mixed into power blending coal and smelting coal or used for smelting nonferrous metals and the like. This process results in the loss of large amounts of high purity silicon and graphite, along with other environmental contaminants.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a method for separating and recovering high-purity graphite and silicon in a waste graphite assembly produced by silicon crystal by utilizing a reselection and flotation method in a mineral processing technology.

In order to solve the technical problem, the gravity separation-flotation combined separation method for graphite and silicon provided by the invention comprises crushing and screening, gravity separation, ore grinding and flotation, and specifically comprises the following steps:

(1) crushing and screening: crushing the graphite component to-2.5 mm by adopting crushing equipment, and screening to obtain two products of +0.5mm and-0.5 mm;

(2) and (3) reselection: adding the product with the diameter of +0.5mm into a shaking table for sorting, wherein the obtained concentrate end product is a silicon particle product, and the tailing end product is an intermediate product of the silicon-containing graphite intergrowth;

(3) grinding: grinding the intermediate product of the silicon-containing graphite intergrowth to an ore ground product with-0.5 mm particles accounting for more than 96 wt%;

(4) flotation: and combining a product with the diameter of-0.5 mm obtained by crushing and screening with an ore grinding product, and performing flotation separation to obtain a graphite product as concentrate and a silicon product as tailings.

As a modification, in step (1), the crushing apparatus used is a conventional hammer crusher.

As an improvement, in the step (2), the product with the thickness of 0.5mm is added with water to be prepared into ore pulp with the concentration of 15-20wt%, and then the ore pulp is fed into an ore feeding groove of a shaking table for sorting.

As an improvement, in the step (2), the process parameters of the table sorting are as follows: the stroke of the bed surface is 9mm-12mm, the stroke frequency of the bed surface is 300 times/minute to 390 times/minute, the water supplement amount is 14 liters/minute to 17 liters/minute, and the transverse inclination angle is 6 degrees to 9 degrees.

The invention has the beneficial effects that: the method effectively recovers the graphite and the silicon in the waste graphite assembly in the silicon crystal production process, the carbon content of the recovered graphite is more than 97%, and the recovery rate is more than 85%; the silicon content of the silicon product is more than 98 percent, and the recovery rate is more than 90 percent. The method has the advantages of low cost, stable and reliable product quality, continuous large-scale production, no environmental pollution and realization of cyclic utilization of carbon and silicon resources.

Detailed Description

Example 1:

a layer of silicon crystal is firmly adhered to the surface of the waste graphite clamping flap and the waste graphite cap seat in the production process of certain silicon crystal. High-purity graphite; the polysilicon is solar grade, and the purity is above 99.9999%. The carbon content in the waste graphite assembly was 56.54% and the silicon was 43.46%.

The gravity separation-flotation combined separation method for graphite and silicon provided by the invention comprises the following steps: crushing and screening, gravity separation, ore grinding and flotation, and specifically comprises the following steps:

(1) crushing and screening: crushing the graphite component to-2.5 mm by using a hammer crusher, and screening the graphite component to obtain two parts of products of-0.5 mm and +0.5 mm;

(2) and (3) reselection: adjusting the pulp of the product with the diameter of +0.5mm to 20wt% by using water, and carrying out table concentrator separation, wherein the process parameters of table concentrator separation are as follows: the stroke of the bed surface is 12mm, the stroke of the bed surface is 350 times/min, the water supplement amount is 17 liters/min, the transverse inclination angle is 9 degrees, the obtained concentrate end product is silicon, and the tailing end is an intermediate product of the silicon-containing graphite intergrowth;

(3) grinding: further finely grinding the intermediate product containing the silicon-graphite intergrowth until-0.5 mm particles account for 97wt% to obtain an ore grinding product;

(4) flotation: the-0.5 mm product obtained by crushing and screening is combined with the ore grinding product, and the concentration of the ore pulp is adjusted to 7wt% by water. Water glass dispersant, diesel oil and No. 2 oil are used as collecting agent and foaming agent, and the process includes twice rough concentration, once fine concentration and once scavenging. And combining refined 1 tail and swept 1 refined and discharging to crude 2 raw ore. The test results are shown in Table 1. The overall recovery of carbon was 85.04% and the overall recovery of silicon was 93.42%.

TABLE 1 flotation test results

Example 2:

the composition of the waste graphite assembly is the same as that of example 1, and the procedure of example 2 is different from that of example 1 in that: in the step (4), flotation separation adopts two times of rough concentration, two times of fine concentration and one time of scavenging. And combining the fine 2 tailings, the fine 1 tailings and the sweep 1 fine to feed in the sweep 2 sections. The test results are shown in Table 2. The overall recovery of carbon was 95.24% and the overall recovery of silicon was 91.32%.

TABLE 2 flotation test results

Description of the drawings: the-2.5 mm, -0.5mm listed in the present invention means particles having a particle size of less than 2.5mm or 0.5 mm; +0.5mm means particles with a size greater than 0.5 mm.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims

1. A combined gravity-flotation separation method for graphite and silicon, which is characterized by comprising the following steps: crushing and screening, gravity separation, ore grinding and flotation, and specifically comprises the following steps:

(1) crushing and screening: crushing the graphite component to-2.5 mm, and screening to obtain two products of +0.5mm and-0.5 mm;

2. The combined gravity-flotation separation method of graphite and silicon according to claim 1, characterized in that: in the step (1), the crushing equipment used is a hammer crusher.

3. The combined gravity-flotation separation method of graphite and silicon according to claim 1, characterized in that: in the step (2), the product with the thickness of 0.5mm is added with water to be prepared into ore pulp with the concentration of 15-20wt%, and then the ore pulp is fed into a shaking table for sorting.

4. The combined gravity-flotation separation method of graphite and silicon according to claim 1 or 3, characterized in that: in the step (2), the process parameters of table sorting are as follows: the stroke of the bed surface is 9mm-12mm, the stroke frequency of the bed surface is 300 times/minute to 390 times/minute, the water supplement amount is 14 liters to 17 liters/minute, and the transverse inclination angle is 6 degrees to 9 degrees.